1. Field of the Invention
The present invention relates to a focusing rear-focus conversion lens device which can be generally used for various telephoto lenses.
2. Description of the Prior Art
Various automatic focusing methods of photographic lenses are known. Various lenses for single lens reflex cameras which can be automatically focused are commercially on the market. However, such a lens allows automatic focusing of only a specific type of lens and is a special lens for automatic focusing. A lens of this type, therefore, cannot be used as a general-purpose automatic focusing lens and is moreover expensive. When a fast-moving object is photographed with a telephoto lens, since the depth of field of the telephoto lens is shallow, framing and focusing cannot be simultaneously performed in accordance with the fast movement of the object. In addition to this, since a telephoto lens is generally darker than a standard or normal lens, it has a lower focusing precision and a longer response time. For this reason, a simple automatic focusing apparatus which has a shorter response time is required especially for use in telephoto lenses.